1. Field of the Invention:
This invention relates to isocyanate-uretdione compounds and a method for their production.
2. Description of the Prior Art:
Aromatically substituted uretdiones, and their production through the dimerization of aromatic isocyanates with tertiary amines or phosphines as catalysts, have been known for a long time. Surprisingly enough, however, aliphatically substituted uretdiones were described for the first time in DE-OS No. 16 70 720.
The aliphatic uretdiones prepared according to the teaching of DE-OS No. 16 70 720, to be sure, contain a considerable amount of the corresponding isocyanurates as an impurity. For example, aliphatic uretdiones prepared according to Examples 1, 2a, 2b and 2c contain 40% butylisocyanurate, 49% ethylisocyanurate, 59% ethylisocyanurate, and 79% ethylisocyanurate, respectively, as impurities.
Further, experiments involving the dimerization of 2-methyl-1,5-diisocyanate-pentane (MPDI), which, if necessary may contain up to 12% by weight of 2-ethyl-1,4-diisocyanate-butane (EBDI), according to the method described in DE-OS No. 16 70 720, led to a reaction mixture having a content of uretdione of only about 30%, by weight.
The oligomerization product of 2-methyl-1,5-diisocyanate-pentane (MPDI) having a high content of dimers has significant utility in the subsequent reaction with diol compounds for the manufacture of valuable starting materials for polyurethane chemistry. However, to date such a product has not been attained.
Therefore, a need continues to exist for such uretdione compounds which have a high uretdione content and a relatively low content of impurities.